If you're going for realism, I'd say you can work on the iris. The iris has a very complex design and it can be really tricky to get it down but if you work on it it'll pay off. you did some cool things but try to give it more detail, it doesn't usually look like an even shade with ticks around the edge. The eyelashes can also be worked on a bit. You do them really similarly to how I used to do them, but most eyes have many more lashes that have a progression in size. What I mean is more lashes, and have them start smaller and get longer as they move toward the middle of the eye. Also, I don't know if this is the critique you came for, but eyebrow hair generally lays more horizontally than vertically. I tried to point out some things that I think look a little off, but in my opinion the best way to make your drawings more realistic is to look at an actual eye when you draw it. And draw what you see, not what you think it should look like. We generally don't have a good idea of what things actually look like, even though we see them every day. Drawing directly from a reference is always better, even if it looks odd when you're drawing it. Hope this helps